How to prune your trees

It is normal for bleeding trees to exude sap when the temperature is above freezing. When pruning trees, make the cut just above the branch collar.(Photo: Courtesy of Brown County University of Wisconsin-Extension)

Take advantage of this week’s above-freezing temperature to schedule your tree pruning. Pruning helps maintain the size of the tree, allows better light penetration into the crown, minimizes disease occurrence, promotes better bloom, increases the safety by removing dead and broken branches, and enhances the overall appearance of your trees.

1) What branches should I prune on young trees?

Prune any crossing branches, water sprouts, root suckers, and double leaders. Remove some of the lower branches to raise the crown. When pruning a limb, make a clean, sharp cut just outside the branch collar (trunk tissue that surrounds the branch base at the point of attachment). Don’t leave a stub. Prune scaffold branches that are too closely spaced on the trunk. Scaffold branches are the large branches that form the main structure of the tree crown. Scaffold branches should be spaced equally to about 12 to 18 inches apart and should be evenly distributed around the trunk and should have wide crotch angles. As a general rule of thumb, don’t remove more than 1/3 of the total crown of a tree at one time.

Yes, you can. Pruning deciduous trees such as maples, birches, black walnut, beech, hornbeam, willow, and yellowwood when the temperature is above freezing produces excess sap flow from the newly cut ends. But don’t get alarmed when you see those cut ends bleed. Although they are unsightly to look at, they don’t cause any harm to the tree’s health.

3) Do newly planted trees require pruning?

Unless the branch is dead, diseased, or damaged, newly planted trees should not be pruned. Pruning newly planted trees can lead to reduction of the foliage which produces the nutrients necessary for new root development and establishment. You can start pruning the tree once it gets established (about two to five years).

4) How should I prune larger limbs?

Larger branches should be pruned carefully to avoid tearing of the bark, for better wound closure and for personal safety. Use the three-point cut method when pruning larger limbs. In this technique, the first cut should be made 12 to 18 inches from the branch’s point of attachment and should be an undercut that reaches half way through the branch. This relieves the weight of the branch. The second cut should be made just outside the first cut and should be pruned all the way down, severing the major portion of the branch completely. The third cut should be made just above the branch collar that removes the remaining branch stub. Do not apply any pruning paint at the cut end of the branches. Always disinfect your pruning tools with 70 percent rubbing alcohol solution before pruning.

5) Do the cut ends need to be coated with tree paint or wound dressing?

No. Tree paint or wound dressing delays the closure of the tree’s wound and can also lead to decay of the tissue. These compounds are recommended only if pruning oak trees during the growing season.

For horticulture-related questions and advice, contact Brown County UW-Extension’s Horticulture Help Desk at 920-391-4615 or bc_uw_extension_horticulture@co.brown.wi.us.

Vijai Pandian is the horticultural agent/educator for the Brown County University of Wisconsin-Extension.